1. Field of the Invention
The invention relates generally to the field of instruments used to make measurements in subsurface wellbores. More specifically, the invention relates to structures for mounting shock and vibration sensors in such instruments to provide a more accurate indication of shock and vibration actually experienced by such instruments.
2. Background Art
Certain types of instruments are used to make measurements from within wellbores drilled through subsurface rock formations. Such instruments may be conveyed through the wellbore by various devices known in the art including armored electrical cable (“wireline”), slickline, coiled tubing, production tubing and by drill string. In the latter conveyance, certain of such instruments may be configured to make measurements during the actual drilling of the wellbore. Moving instruments along the interior of a wellbore, in particular during drilling, as well as handling and transportation to the well site, can impart shock and vibration to the instruments.
There is a need to properly characterize the shock and vibration levels that such instruments experience. Only through proper characterization of the shock and vibration environment to which such instruments are exposed can more accurate shock and vibration testing specifications be developed. More accurate shock and vibration testing specifications may assist in the design of more robust wellbore instruments.
A shock and vibration environmental recorder has been developed for placement inside a wellbore instrument. One such recorder is sold under model designation “SAVER 3×90” by Lansmont Corporation, Ryan Ranch Research Park, 17 Mandeville Court, Monterey, Calif. 93940. The shock and vibration recorder generally consists of triaxial accelerometers, analog to digital converters and appropriate analog and digital processing circuitry and digital memory or other data storage to store the measurements made for a selected time period.
However, such recorders cannot simply be placed in or on a tool and accurately characterize the shock and vibration experienced by the instrument. The sensing elements in a shock and vibration recorder are typically accelerometers that are mounted on a circuit board. The circuit board having the accelerometers must be mounted inside the instrument housing in a way that assures adequate mechanical coupling between the instrument housing and the circuit board.
It is known in the art to directly mount accelerometers and strain gauges directly on the instrument housing. While effective, such mounting can make servicing the instrument more difficult and expensive.
There exists a need for devices to mount shock and vibration sensors (e.g., accelerometers) that make instrument assembly convenient and accurate, and provide sensor mounting to the instrument housing that efficiently transfers acceleration from the housing to the shock and vibration sensors.